Thermostat



F. KUAHN ET AL Feb. 16, V193.7.

THERMOSTAT FileFeb. 15, 1952 ATTORNEY-S' Patented Feb. 16, 1937 2,070,604`

\ *d uNlTEDsTATEs VPATENT ori-ICE THERMOSTAT rFrank Kuhn, Detroit, and LaurenceH. Thomas, Birmingham, Mich., assignors to American A Electrical Heater Company,v Detroit, Mich., a.

corporation of Michigan vApplication February-15,1932', serial No'. 593,170 I toning.' (ciels-25) The invention relates to thermostatsdesigned thin bottom portion E between'the same andthe for use in connectionk with electrical heating deironing surface. F` is a thermostatic electric vices and to 'control the temperature thereof'by switch located within the recess D and so posithe opening and closing of theA heating circuit. tioned as to receive heat for its operation through The invention is more particularly adapted for. the medium of the thin bottom portion E. As 5f use in connection with laundry irons and has for this bottom portion E is not in direct contact with its-object a more exact regulation of the temper-v the heating element B it must receive its heat from ature in accordance tothe work being performed. the surrounding portion of the base A.r Also by In electrically heated laundry irons it is vusual reason of the fact `that its -pointof juncture with to place the heating unit above the base of theA the surrounding portion ofthe base is onlyA slight- 1d viron, the heat being transmitted by conduction 1y above the ironing surface, its temperature will through said base to the lower or'ironing surface be'substantially that of the ironing surface which thereof. The temperature of this ironing surface is always lower than that of the upper portion of depends rst upon the rate of generation of heat the base. f l5 in the unit, and second, upon the rate of dissi- Various specific constructions of ,thermostatic 15 pation or absorption in performing the work. switches may be employed, it being only essential y Thus if the articles being ironed are relatively that thetemperature for operationshould bedevdry the rate of heat dissipation will be correrivedthrough the medium of the portion E. Howspondingly low. On the other hand, where the ever, as shown, the construction is as follows: AG

v articles containa greater amount of moisture, the is a thermostatic element suchzasua composite 20 heat dissipation is more rapid and thetemperametal bar, one face of which normally lies in close ture of the ironing surface willbe lower. One of proximity to the top face of the bottom E, being the principal diiiiculties in satisfactorily controlsupported in this position-from the top casing A' ling thetemperature of the iron by a thermostat -through the medium'of a depending bracket arm is not only to lprevent overheating where the ra'te A2. The supported'end of the thermostatic bar 25 of dissipation is low, but also to maintain a sufliis attachedtoa blockfH upon which isA mounted ciently high temperature in the ironing surface the electric switch. This switch comprises are--v when the rate of heat dissipation is high. silient strip I carrying at its outer end one ofthe The present invention is adapted to overcome contacts J and above the strip I and insulated this difficulty by a construction inwhich the heat therefrom is a second resilient strip K carrying 30 for operating the thermostat is transmitted thereat its outer end a cooperating contactL. `The to through a medium in close proximity to the strip K has an extension M whichris bent downheat dissipating surface. Thus instead of mainward and has a mechanical contact N adjacent to taining a uniform temperature at the point of the thermostatic bar G. All. of these parts are heat generation, the control temperature is that clamped to and supported by the bracket arrnAZ. 35

of the heat dissipating surface and where the rate Thus as sov far. described, whenever vthe temperof dissipation is high, a higher temperature will ature of the barG is raised sufficiently by rheat be permitted in the heat generating element. conducted thereto through thethin bottom por'-v While the invention is applicable to Various tion E, this'bar'G willwarp yupward and through 4o heating devices as well as laundry irons, the latter the medium of the mechanical contact N and ex-v 40 only is described and illustrated in the accomtensionMwlll raise the flexible stripKseparating panying drawing in which the contact L from the contact J and interrupt- Figure' 1l ls a longitudinal section through a ingthe electrical current. portion of a laundry iron showing the thermostat `It is desirable to prevent too frequent opening applied theretO; s and closing of the switch or what is termed .flut-A 45 Figure 2 is a cross section on line 2---2v of Figtering, as this has a tendency to burn out the ure l; contacts and also. to produce disturbance in any Figure 3 is a view similar to Figure 1 showing Aradio apparatus in the vicinity. .I'o accomplish the parts in the different positions of adjustment. this result, a second thermostat is employed, this The laundry iron to which the thermostat is being operated by electrical `heat generated'di- '50k applied comprises a base portion A above which vrectly therein. As shown, the second thermostat is placed a heating unit B secured thereto bythe is a composite bar O secured to a portion of the heat distributing and clamping plate C. D isa flexible strip K and adapted when heated byY recess extending through the plate Cr and downelectrical current flowing therethrough to warp `ward in the base A, leaving only a comparatively said strip inward vso as to causer the contact L to g5 c move-towards, the contact J. When the iron is lJ are closed the bar Owill be electricallyheatedr cool the stripO will be warped outward and the contacts L and J will notfbe closed until the thermostatic bar G is warpedv downward a suicient distance; IHowever, as soon as the contacts L and lsoas to be warped in ardownward direction and consequently the switch will not be open untilthe temperature falls somewhatwlower than the temperature at which` the switch `was. closed. This will-eiectually prevent iluttering.

To regulate the temperature at which the thermostat operates, there is provided a .suitable adjusting devicesuch as the cam P having a screw threaded shank Q engaging the bracket A2,'.and an i operatingr handle r1%. above the casing A" of Ythe iron. cam P kforms va stop iorengag ing av post S on the resilient strip'Iand'byadiusting l 'the cam the' position of the stop isfaltered. f

Theelectrical current Vis conducted to the therc Y mostat through suitable terminal posts T and T clampedrespectively `in contact with the strips I and K and insulated froml each other bythe intermediate insulating stripjU. An insulator strip Vis also preferably placed between the resilient strip I and the'thermostatic barl G to avoid any accidental electrical connectionmbe'tween these members.

j With the construction above described, the lo- .cation ofthe thermostaticelement G is such as to be shielded from, all heat of the iron other Ythan that derived from the thin bottom portion E which in turn vmust receive its heat by conduction from" the portion ofthe base A which is adjacentto the ironingsurface. VThus whenever the iron is being y used on a wetV garment-which` rapidly absorbs the c heatfrorn the ironi'ngfsurface, thethermostatic 'switch will remainy closed even though the :ternperature of the heating unitmayb'e considerably Vhigher thantheopening temperature .of the switch. VIn otherj words, the-switch responds to VtlieQltemperatureol thezironing surfacev rather than tothe temperatureof any other part of Ythe n iron.

Atained at a temperature'for emcientlyfperform- Thus While-the ironing surface. is ,atl all times Aprotected from. overheating, it is main- Someof the subject-matter disclosed but not' claimedin this application 'is claimedV in our copending application; Serial y No. 751,594',` lilled `Whatweclaim'as our invention is:-

'1. Anfelectriclaundry iron jcomprisinga heat distributing base of substantial thickness having a recess forming athin bottom surface of substantially' uniform thickness, a heatingelement conl tacting with the upper surface 'of said base, a pressure plate' above said heatingelement having an opening extending completely. therethrough registering with lthe recess-in said base, a frame securedto said iron independently of said pressure plate and base plate and independently removable, said frame having aportion depending within the Vopening in ysaid pressure plate, a'bimetallic Ythermostatic barhavingone endV thereof rigidly con- "nected tothe depending portionvof said frame,

said thermostatic bar extending laterally from.

. vsaid support in substantial contact with the upper l u temperature of said bar is determined by the'tem- 'perature of said thin bottom portion substantially 'V independently of the temperature of the remain--l Y 75 surface Vof said thin bottom iportion and adapted to ywarp in a direction away from said bottom portion upon increase in temperature whereby the ingv portionsvof the said base and said pressure plate,a non-thermostatic member operatively engaging the free end of said thermostatic bar to Vbe moved thereby and a switch within said recess'` automatically operable by the ,movement oisaidh`V non-thermostatic member for energizing and de.

energizing said he'atingelement in accordance y withthe temperature of said thin bottom portion.

2.y An electriclaundryI ironcomp'rising a heat distributing base' of substantial thickness having Y a recess forming Aa thinbottom surface `oi sub-L stantially uniform thickness, a heating element contacting with the upper surface of said base,V ya rpressure plate above said heating plate having l an opening extending Y f. completely therethrough registering with the recess in said base, a frame mounted independently rof, said pressure plate mounted to said iron, said .frame having a portion depending withinthe opening in said pressure plate and extending into said recess in said base y plate; a lbimetallic ,thermostatic bar having onek end thereof rigidly connectedv tothe depending and said base plate and quickly detachably portion of said frameL and extending laterallyQ fromsaid frame .parallel to vand in substantial contact with the upper. surface of said thin kbot-A tom portion, said thermostatic bar being adapted'to warp ina directionv away from saidbottorn Y' portion upon increase in temperaturea pair oi? springstrips also secured to said depending portion ofsaid frame, contacts carried'byfsaidf spring stripsand arranged within said' recess, an j Y adjustable kabutment carried by saidv frame for' Vlimiting the upward movement offone ofsaid.

spring stripsand means operativelyconnecting said .thermostatic bar with the' other of said spring .strips to separate said contacts 'upon'predetermined upward warping of said therrnosytaticf bar..

3. An electricflaundry iron comprisingfaheat distributing base of substantial thicknesshaving .l

atY

a recess forming a thin bottom surface of sub"v l stantially .uniform thickness, a heating element contacting with the upper surface of saidbase, a.y

pressure plate yabove said heating element hav 'ing .an openingr extending completely there-F through registering with the recess in said base, a ftop casingarframe secured .to said top casingindependent of directconnection to said base plate and pressure plate and removable with' saidtop n casing, said' frame having a portion dependingV withinthe opening inA said pressure plate, abimetallic thermostatic bar havingyone end .there` of rigidly connected tothe depending kportion Y of Asaid frame, said thermostatic barextending laterally from said support in close proximity to the uppersurface of; said,thinbottomportion and adapted to warp in one direction `upon in-` crease in temperature wherebyfthetemperature of said bar is determined by ,the temperature of said thin bottom portion substantially independently ofthe `temperature of the remaining .Y

portionsof the said base and said pressure plate. a non-thermostatic member operatively engaging the free end ofsaidthermostatic bar to be moved thereby and a switch within said recess autoy matically operable by the movement of said nonj 'thermostatic member forl energizing and de-en-vv ergizingsaid heating element in accordance with thetemperature of said thin bottomy portion.

v4. An electric laundryiron comprising a heat distributing baseiof substantial thickness having arecess forming a thinfbottompsurface off substantially. uniform thickness, va Yheating element contacting with the upper surface of said base, a pressure Vplate above said heating element having an opening extending completely therethrough registering with the lrecess in said base, a frame secured to said iron independently of said pressure plate and base plate and independently removable, said frame having a portion depending within the opening in said pressure plate, a bimetallic thermostatic bar having one en d thereof rigidly connected to the depend# ing portion of said frame, said thermostatic bar extending laterally from said support in substantial contact with the upper surface of said thin bottom' portion and adapted to warp in one direction upon increase in temperature whereby the temperature of said bar is determined by the temperature of saidthin bottom portion substantially independently of the temperature of the remaining portions of the said base and said pressure plate, a non-thermostatic member operatively engaging the free end of said thermostatic bar to be moved thereby and a switch within said recess automatically operable by the movement of said non-thermostatic member for energizing and deenergizing said heating element in accordance with the temperature of said thin bottom portion.

5. An electric laundry iron comprising a heat distributing base of substantial thickness having a recess ifo ing a thin bottom surface of sub,- stantially uniform thickness, a heating element ing an opening extending completely there' through registering with the recess in said base, a frame secured to said iron independently of said pressure plate and base plate and independently removable, said frame having al portion depend-- ing within the opening in said pressure plate, a bimetallic thermostatic bar having one end thereof rigidly connected to the depending portion of said frame, said thermostatic bar extending laterally from said support in close proximity to the upper surface of said thin bottom portion and adapted to warp in a. direction 'away from said bottom portion upon increase in temperature whereby the temperature of said bar is deter-I mined by the temperature of said thin bottom portion substantially independently of the ternperature of the remaining portions of the said base and said pressure plate, a non-thermostatic memberoperatively engaging the free end of said thermostatic bar to be movedy thereby and a switch within said recess automatically operable by the movement of said non-thermostatic member for energizing and deenei'gizing said heating FRANK KUHN. LAURENCE H. THOMAS. 

